Art of winding coils



flr h W49" H. v. KNAUF, JR

ART OF WINDING COILS Filed. July 31, 1946 4 Sheets-Sheet l i INVENTOR GU14 \[Knuui 1 v.

ATTORNEY III/2011111171221)? H. V. KNAUF, JR

ART OF WINDING cons III/III]! III/111x01 III/ll! Filed July 31, 1946 INVENTOR drrg V Kmuf Jr.

ATTORNEY @pt fi, W49- H. v. KNAUF, JR

ART OF WINDING COILS 4 Sheets-Sheet 4 Filed July 31, 1946 M R L H m u .N N G R E n. 0 ME VA 4 Q M Q m g Q Q 1 I. @M Q Q Q Q M 3R E Q QN R m: Rx wk p x Rumu .3 mm mm ww Patented Sept. 6, 1949' UNITED ART OF WINDING COILS Harry V. Knauf, .lr., Oaklyn, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application July 31, 1946, Serial No. 687,447

I This invention relates to the art of winding coils, particularly form-mounted inductance coils and. while not limited thereto, will be described as applied to the manufacture of voice coils" for loudspeakers.

Loudspeaker voice coils usually comprise either a single or plural layer helix wound upon a cylindrical impregnated-paper form which is no thicker than, say, 0.005 of an inch. When made by mass production methods such coils have heretofore been wet-wound, i. e., the adhesive impregnant which binds the wire and the coil form into a unitary structure-is applied in a highly fluid state during the winding operation and is subsequently evaporated, as in a drying oven. Wet-winding is an untidy procedure and is an expensive one as well. Furthermore, wet-winding results in an unusually high percentage of rejects. Why this is so will be apparent when it is appreciated that since the bonding agent must be applied in an extremely fluid condition it can contain only a small percentage of solid adhesive material, hence the strength of the bond between the parts is relatively poor even in those units which are thoroughly dry and otherwise perfect. Through drying is not always achieved in practice because a wet-wound coil immediately acquires a surface skin which traps the liquid solvent and renders his escape difficult even under accelerated drying conditions.

Incompletely dried coils may retain the trapped solvent for many months and when such a. coil is subject to normal vibrational stresses (1. e., in the audio frequency range of from, say, 30 to say, 10,000 cycles per second) its turns may creep and ruin the performance of the loudspeaker. Prolonged drying, on the other hand, may cause the coil form to shrink and the coil to warp, making it necessary to expand the form in an effort to restore the assembly to its original shape and dimensions.

Accordingly, the principal object of the present invention is to obviate the foregoing and other less apparent objections to present day wetwound coils and to provide an improved method of and apparatus. for winding voice coils and analogous (form-mounted) inductors.

Another and related object of the invention is to provide an improved method of and apparatus for the dry-winding and embedment of coils and which, in its practice and use, dispenses -Claims. (Cl. 154-80) with all auxiliary moulding and other shaping procedures and mechanisms. (Cf. the 1924 British Patent No. 250,282 to Rickets et al.)

The foregoing objects are achieved in accordance with the method of the present invention, first by making, on a mandrel or arbor, a coilform having a dry coating of a synthetic resinous thermosetting adhesive material in an intermediate stage of fusibility on its outer surface, then heating the coating material (as by heating the arbor) to render said coating tacky, then winding wire having a similar (dry) adhesive coating on the said form whereby the coating on the wire is rendered tacky by contact with the heated surface of the coil form, and then heat-setting both coatings to the infusible stage.

Certain preferred details of procedure and construction, together with other objects and advantages of the invention will be described in connection with the accompanying drawings wherein: I

Fig. 1 is a view in perspective of a multiple coil winding machine constructed in accordance with the principle of the invention and including a detached cylindrical split-sleeve for making a coil form and a tool for removing said sleeve from the heated mandrel of the machine.

Figs. 2, 3 and 4 are end views of the split sleeve of Fig. 1 showing the manner in which the sheet material, of which the coil form is made, is wrapped.

Fig. 5 is a fragmentary view in perspective of the machine of Fig. 1 showing the sleeve of Figs. 1 to 4 on the heated mandrel and undergoing a rolling operation for bonding the layers of sheet material together.

Fig. 6 is a longitudinal sectional view revealing the construction of the heated mandrel of the machine.

Fig. 7 is an enlarged view in perspective of on of the wire-guiding and holding means of the machine.

Fig. 8 is a view in perspective showing the winding machine in operation and including the reeling system from which the wires are fed to the coil form.

Fig. 9 is an enlarged side elevational view partly in section'of one of the supply reels of Fig. 8 and Fig. 10 is an enlarged fragmentary view in perspective of the machine upon the completion of the winding movement, with the wires broken off and held in a position to permit-the removal of the coil form from the mandrel.

In applying the invention to the manufacture of voice coils, it is preferable to start with a high grade kraft paper, say, 0.0006 to 0.0015 of an inch thick, and with enamel covered copper wire, of the desired gauge, and coat the paper and the wire, separately, with the thermosetting adhesive material which is allowed to dry at room temperatures to a point where all of its volatile constituents have evaporated. Any of numerous resinous adhesives having the property of becoming tacky at an elevated temperature which is lower than is required to set, or render it infusible, may be employed as the coating material. In general, all A-stage" condensation type thermosetting resins possess this desired characteristic. The adhesive properties of the coating material may be enhanced by the addition of a thermoplastic adhesive such, for example, as a vinyl resin. One satisfactory coating material formula is:

Ethyl alcohol (solvent) 1200 By one step phenolic resin is meant a phenolic resin in that incomplete stage of condensation (commonly known as the A stage) wherein the resin is still fusible and completely soluble. (When parts A and B of this formula are mixed there is a tendency to separate, thus the material should be agitated during the coating process.) Other, ready-mixed, thermosetting adhesives are available under various grade marks. One entirely satisfactory proprietary material is Bostick Cement 7008 sold by B. B. Chemical Co. of Cambridge, Massachusetts.

The dry adhesive-coated paper I from which the coil forms are made tends, usually, to curl up on its coated side I a. Since the adhesive must be on the outside of the finished form it is necessary or expedient to counteract this tendency,

on, the electrically heated rotating arbor 3. The

, heat transferred through the sleeve 2 to the paper from the electrical heater element 6 (see Fig. 6) is just sufiicient to soften the adhesive coating on the paper. Thus, when the handle a on the bracket 5 is pulled down (as shown in Fig. 5), the roller 4 is brought into contact with the paper and applies a rolling force which bonds the tacky layers of the paper together into'a smooth, composite cylindrical structure. When the rolling operation is completed the roller 4 is thrown back and the tacky paper is ready to receive the wire or wires.

Any number of coils within'the limits of the length of the winding arbor 3 may be wound simultaneously. As shown in Fig. 8 the machine is set up to wind nine coils. Here the nine supply spools'Sl-SS are supported in equally spaced relation on a triangular frame 1 above and to the rear of the arbor 3 and the individual wires -Wl-W9 .are led down around fixed rollers either by tension (e. g. by running it over a smooth, warm surface and then wrapping it on a, cylindrical form) or by curling the sheet in the reverse direction, as by inserting it in the slot from unwinding before the sleeve is placed on the coil winding machine, by heating the coated surface at spaced oints along its edge. This "spot tacking operation can be done simply by touching the wrapped paper to the electrically heated mandrel or arbor 3 of the winding machine. The machine shown in the drawings is especially constructed for the commercial practice of the method of the invention and is provided with a rubber or similar roller 4 which is mounted in register with the arbor 3 on a pivoted bracket or frame 5 so that the roller may be brought into contact with the rolled paper when the sleeve 2 upon which the paper I is wrapped is mounted Rl-Rs and thence forward and upward over grooved guide members M l-M9 on a rod 3 which is mounted for axial movement, parallel to the axis of the arbor 2, under the control of a hand lever Do on the base of the machine. In setting up the wires Wl-W3, prior to the winding operation, the free end of each wire is held upright each by a spring cli 3 (see Fig. 7) on the outer face of the alternate (odd-numbered) of ten pairs of wire guiding "fingers Fl to F20 which are mounted on a rod it carried by a pivoted frame ll beneath the arbor 3 of the machine. As shown in Fig. 9 the axle of each supply spool Sl etc. is provided with a clutch l! to facilitate replacement of the spool and with a friction brake l3 for maintaining tension on the wire throughout the winding operation.

After the coil form has been rolled and the roller 4 moved out of the way, each wire is removed from its clip 9 and placed on the tacky surface of the coil form slightly to the left of the odd-number finger, to provide an extra length of wire which when removed from the coil form comprises an attaching lead for the coil. As soon as the wires are brought into contact with the heated surface of the coil form they are held fast by the tacky adhesive thereon. The operator then raises the handle Ila of the pivoted bracket II and thus brings the wire guiding fingers Fl-F20 adjacent to, but not touching, the rotatable heated arbor 3 upon which the sleeve 2 for coil form I is mounted. The fingers Fl etc. are maintained in the raised position, shown in Fig. 8, by means of a counter-weight ll (see Fig. 1) and an over-center spring I! (see Fig. 8) which is secured at one end to the rod l0 and, at its other end, to the base It of the machine. The lever 8a is then moved to the right. This shifts the axially movable rod 3 upon which the rooved wire guides Fl etc. are secured, to the left, and brings thesaid guides into the starting position.

When all wire ends have been removed from the clips 9 and applied to the coil form I, and the lever Ila has been raised, the arbor 3 is rotated through as many revolutions as required .to form a coil of the desired number of turns. As shown in Fig. 1 the power required to rotate the arbor 3, and to operate its conventional revolution counter I] may be applied either by means of a hand-wheel l3 or by a belt l3. In the latter case the belt may be driven by'an electric motor (not shown) under control of a foot actuated switch (not shown).

The limits of the length of the individual coils Cl, C2, etc. are determined by the spacing of the paired fingers Fl-F2, F2-Fl, etc. As previously set forth, the rod 2 upon which the grooved wire guides Ml etc. are mounted can be moved axially with respect to the fingers Fl etc. and the arbor I, under the control of the lever or arm la.-- Hence, when winding a voice coil or similar plural layer structure, it is merely necessary to move the pivoted arm in to the left at the time the wire comprising the lower layer reaches the side of the even-number fingers (F2, F4, etc.) in order to start the second or reverse-wound layer. This movement of the arm to to the right moves the rod 2, which carries the grooved wireguides Mi etc., to the right. Obviously, the

spacing oi the turns comprising either layer may be regulated, if desired, by changing the rate of movement of the lever 8a as by means of a cam (not shown). In this latter event it is preferable to mount the rod 8 somewhat closer to the arbor than is shown in the drawings.

In Fig. 8, the rod 8 has reached the limit of its movement in the return (left) direction. That is to say, the wires Wl-W2 etc. have reached their starting point adjacent to the faces of theodd-numbered fingers Fl, F3, etc., and the winding operation has been completed. While the bar ill is still in its raised position the operator pulls each wire over the end of the adiacent (odd-numbered) finger Fl, F3, etc., and, by so doin places it under the spring clip 9 on the said finger, and then severs all of the wires, simultaneously, simply by pulling down the handle Bio of the pivoted supporting frame ll against the biasing force of the counterweight it and oil-center spring i5 (Fig. 8). As shown in Fig. 10, the arc of movement of the frame ii upon which the guide fingers Fl, etc. are mounted is such that, when it is pulled down, the freeends of the wires Wi, W2, etc. are held in a readily accessible upright position and the coil ends of the wires are conveniently tacked" to the adhesive on the coil form I by the force applied to the wires during the severing operation.

In order to remove the sleeve 2 upon which the coil form I is mounted from the arbor 3 it is first necessary to release the bearing at the outer end of the arbor. This is done by turnin two thumbscrews 2| and 22. The upper screw 2| releases the shaft 23 upon which the said bearing is mounted and the lower screw 22 releases the upright 24 which supports the said shaft, thus permitting the said support 24 to be pivoted towards the rear, out or the way of the arbor 3. When the metal sleeve 2, upon which the paper coil form is mounted, has a tight fit on the arbor 3, its removal from the arbor is facilitated by using the pincer-like tool 25 shown in Fig. 1. One of the cylindrical jaws of this tool contains an inwardly extending pin 2501 which is adapted to be received within a helical groove 3a in the arbor. Thus, when the jaws of the tool are closed about the inner end of the arbor and the arbor is rotated (as by means oi the handwheel it) the pin 25a will follow the groove in and urge the sleeve 2 outwardly toward and oil the free end or the arbor.

When, as shown in the drawings, the metal form upon which the paper and coils are wound comprises a split sleeve, the diameter of the said form will be efiectively reduced upon its removal from the arbor 2. 'I'hisobviously'facilitates the removal of the paper coil-form from the said sleeve. However, since it is desirable to mount the still tacky paper-forml on a metal form during the thermosetting of the adhesive. it is usuallyexpedient to employ a conventional (non-split) cylindrical form throughout the winding-operation, since, in this event, the same form may be used during the setting process. In any event, when the winding operation has been completed, the paperform I, mounted on its temporary inner cylindrical metal support, is subject to a temperature'higher than that used during the winding operation in order to set the resinous adhesive coatings on the paper and wire. A conventional oven (not shown) may be used for this purpose. Thereafter the paper coil form may be cut into discrete lengths each individual to a single coil.

It will now be apparent that the present invention provides an improved method of, and apparatus for, "dry-winding" form-mounted coils and, furthermore, ensures a coil structure that will retain its shape throughout the assembly operation and one which is substantially immune to vibration, humidity and temperature changes.

What is claimed is:

l. The method of making a form-mounted coil from a wire, a coil-form, and a dry coating of a synthetic resinous thermosetting adhesive in an intermediate stage of fusibility, which comprises winding said wire upon said coil form while subjecting said dry-coating to a temperature sufficientl high to render said coating tacky yet not so high as to thermoset said adhesive and, subsequent to said winding operation, subjecting said form-mounted coil to a temperature suiilciently high to completely thermoset said adhesive.

2. The method of making a coil from wire having a dry coating of a thermosetting adhesive in an intermediate stage of fusibiiity, which comprises winding said wire upon a heated coilform whereby said coating is rendered tacky and is caused to adhere to said coil-form, and subsequently treating said adhesive so as to render it infusible.

3. The method of making a form-mounted coil with wire having a dry coating of a thermosetting adhesive, which comprises heating said coil form to a temperature sufllciently high to render said dry-coating tacky by contact with said form yet not so high as to render said adhesive completely infusible, winding said drycoated wireupon said heated coil form whereby said coating is rendered tacky and is caused to adhere to said form, and subsequently subjecting said form-mounted coil to a temperature suiliciently high to render said adhesive completely infusible.

4. The method of making a form-mounted coil with wire and a coil-form having a dry coating of a thermosetting adhesive, which comprises heating said dry-coated coil form to a temperature sufliciently high to render said coating tacky yet not so high as to render said adhesive completely infusible, winding said wire upon the tacky surface of said heated coil form, and subsequently subjecting said assembly to a temperature sufllciently high to render said adhesive completely infusible.

5. The method of making a form-mounted coil from wire and a pre-fabricated coil form each provided with a dry coating of a thermosetting adhesive in an intermediate stage of iusibility, which comprises heating said drycoated coil form to a temperature sufficiently high to render its dry coating tacky, winding said 7 dry-coated wire upon said heated coil 10m wherebythe coating on said wire is rendered tacky by contact with said heated tacky surface or said coil term and is calued to adhere thereto. and then subjectinx said form-mounted coil to a temperature suillciently high to render said adherent coatings completely intusible.

, HARRY v. KNAUF, Jr.

REFERENCES CITED The following references are of record in the tile of this patent: 1

, 8 tmrrm sum rams-s Number Saflord Oct. 2, 1934 

